Deborah,
the Dowager Duchess of Devonshire, and the
last surviving Mitford sister, has died aged 94.

Her son,
the Duke of Devonshire, announced the death in a statement from Chatsworth
House, her stately home.

Prince
Charles said he was "saddened" by the news, saying he "adored
and admired" Deborah and would "miss her so very much".

The Mitford
sisters fascinated - and sometimes scandalised - British society in the 1940s.

Unity was a
friend of Hitler; Diana, the second wife of British fascist leader Sir Oswald
Mosley; Jessica, a left-wing activist, and Nancy, a novelist and historian.

Deborah,
like her elder sister Pamela, was more focused on home life.

Nonetheless,
along with her siblings, during her lifetime she moved in the same circles as
Sir Winston Churchill, John F Kennedy and Evelyn Waugh.

She also
accompanied her sister Unity to tea with Hitler in 1937, was painted by Lucian
Freud, and amassed a collection of Elvis Presley memorabilia.

Nicknamed
the "housewife duchess", she made Chatsworth in Derbyshire one of the
most successful and profitable stately homes in England after marrying Andrew
Cavendish - who later became the 11th Duke of Devonshire - in 1941.

The
statement from her son said: "It is with great sadness that I have to
inform you that Deborah, Dowager Duchess of Devonshire,
has passed away peacefully this morning."

It added
that an announcement about funeral arrangements would be made shortly.

Prince
Charles said: "My wife and I were deeply saddened to learn of the death of
the Dowager Duchess of Devonshire, whom both
of us adored and admired greatly.

"She
was a unique personality with a wonderfully original approach to life, and a
memorable turn of phrase to match that originality.

"The
joy, pleasure and amusement she gave to so many, particularly through her
books, as well as the contribution she made to Derbyshire throughout her time
at Chatsworth, will not easily be forgotten and we shall miss her so very much."

Born
Deborah Vivien Freeman-Mitford on 31 March 1920, the duchess was the sixth
daughter of the 2nd Baron Redesdale.

The
Mitfords' childhood at their family home in the Oxfordshire village of Swinbrook
was immortalised in Nancy's
novels, The Pursuit of Love and Love in a Cold Climate.

Her parents
made a poor job of hiding their disappointment that Deborah had not been born a
boy, leaving Thomas their only son.

The
Mitfords' father disapproved of educating girls, famously insisting that hockey
would make their ankles fat, and Deborah spent her formative years skating and
hunting.

Her sister
Unity's infatuation with Hitler saw the young Deborah invited to tea with the
German dictator, although the visit made little impression on her.

"If
you sat in a room with Churchill," she later recalled, "you were
aware of this tremendous charisma. Kennedy had it too. But Hitler didn't - not
to me anyway."

At
Chatsworth, the Duchess took on a major role in running the house and its
garden, which have been used in a number of film and TV productions, and she
ran the estate's farm shop.

In July
2002, the duchess and her husband spoke out against the government's proposed
ban on fox hunting.

Made a dame
in 1999, she became the Dowager Duchess of Devonshire
in 2004 after her husband died and their son inherited his title.

She penned
a number of books including the autobiographical Wait for Me: Memoirs of the
Youngest Mitford Sister, which was published in 2010.

The Dowager Duchess of Devonshire
obituary

Last of the famous
Mitford sisters, she became a successful chatelaine of Chatsworth House

Deborah,
Dowager Duchess of Devonshire, who has died
aged 94, was for more than half a century the chatelaine of Chatsworth House,
the great stately home and estate in Derbyshire. In that time she did much to
promote it as a favourite public destination.

But she
started out as the youngest of the Mitford sisters – the country chick of that
sophisticated brood, the extraordinary offspring of Lord Redesdale and his
wife, Sydney. Although sister Nancy's claim that Debo could imitate a hen
expelling an egg might have been a joke, Debo did drive the cart delivering the
Mitford henhouse eggs to the station. While Nancy, Diana, Unity and Decca pursued
literature, fascism, Hitler and socialism, Debo's best friend in childhood was
the family's old groom, Hooper, "the human end of the horses; the stables
were my heaven".

She was
born at Asthall Manor, Oxfordshire, but equine bliss ended at 16 when the
Mitfords sold their next country house: at 17, Debo's closest sibling, Jessica
– "Decca" – eloped without a word, a letdown slightly ameliorated by
the £1,000 libel settlement the Daily Express paid Debo for wrongly naming her
as the runaway, which she squandered on a fur coat. She came out as a debutante
in 1938 at a ball given by her doting father at the Mitfords' London house, and enjoyed the last real
season before the second world war. Unity, the Hitler groupie, wrote from Germany:
"Swyne [a Debo nickname] seems to be having a wonderful time … who will
the romance be with?"

The answer
was Lord Andrew Cavendish, also 18, younger son of the Duke of Devonshire,
encountered at the races. He joined the Coldstream Guards, while Debo and her
mother went to Berne to collect Unity, who had
put a bullet through her brain but survived, severely damaged; they coped with
Unity's resultant moodiness and incontinence through the first year of war. But
then, nothing organic fazed Debo – when travelling to Mull by train, she milked
her beloved goat in the first-class waiting room at Stirling:
"Which I should not have done since I only had a third-class ticket."

Debo wrote to Diana – in Holloway for
supporting her fascist husband, Oswald Mosley – about her impending nuptials:
"I do wish you weren't in prison. It will be vile not having you to go
shopping with, only we're so poor I shan't have much of a trousseau." Debo
married Cavendish in the bomb-damaged St Bartholomew the Great, in London: "Two houses
had been totally destroyed in our street the night before, and all the glass
was blown out of our house, so my mother put up wallpaper rolls as pretend
curtains and went on with the wedding." She followed him around the
country: "I do disgusting work now, do feel sorry for me, it's in the YMCA
canteen and it's very embarrassing because they all copy my voice," both
its extraordinary vowels and the racy Mitford lingo.

But Debo was never a serious snob,
considering class an irritant: "The biggest pest that has ever been
invented". Her husband became heir to the dukedom on the death of his
brother in 1944 and succeeded unexpectedly early when his father died in 1950,
14 weeks before the date on which the estates would have escaped 80% death
duties. The couple inherited a directory of property, principally Chatsworth
House, with 175 rooms, 50 of them huge, and a £5m revenue bill incurring £1,000
interest a day. It took 17 years to clear the debt, with failed appeals to the
high court and the sale of Rembrandts, a Poussin and superfluous ancestral
accommodation, including Hardwick Hall, also in Derbyshire.

In 1959 they moved in "over the
shop" at Chatsworth, made over to a trust, and they kept an Irish holiday
castle, Lismore. Nancy, a connoisseur of aristocratic chilblains, wrote to
Diana: "Debo has become the sort of English duchess who doesn't feel the
cold." They transferred to Chatsworth to help repair it for the first round
of stately-home-openings. Debo did the decor, the grandest of shabby chic – she
continued the house tradition of gold-leafing the exterior window frames, but
only because it lasted longer than paint and she liked the glow on gloomy
November days.

Nancy teased Debo that invitations to writers and artists to stay had
more to do with interiors than intellect: "They are terrible wreckers,
worse than puppies and will give a mellow old look to the house in no time at
all. I expect that's why you have them." Not quite fair, perhaps: the Duke
commissioned Lucian Freud to paint Debo's portrait when she was 34
("That's the dowager duchess; it was taken the year before she died,"
asserted a visitor); and, although Debo claimed to be no reader and only a
letter-writer, there were corridors stacked with Mitford letters, she wrote a
history of Chatsworth, an estate shop steady-seller, and a wicked collected
journalism volume, Counting My Chickens ... and Other Home Thoughts (2001). She
was an unlikely devotee of Elvis Presley, and King memorabilia decorated her
Chatsworth office. Such a beauty when young, she said; she had visited his
rival stately home, Graceland, and thought it
very moving.

She was a competent businesswoman ("I
am very good at spending money and she is very good at making it,"
conceded the Duke), managing her share portfolio and the Chatsworth
enterprises; hers was the signature printed on the labels of Chatsworth Food
Ltd's chutney and Cumberland sauce; she served in the farm shop "until
they installed the mechanical till which I was too stupid to operate".

But the estate's 6,000 farmed acres, which
Debo could name field by field – Mrs Vickers's Breeches, Big Backsides, Old
Zac's Pingle – stimulated her more than the house's silver steward and the
2,000 lightbulbs, which were powered by an updated wonder of Victorian
hydraulic engineering. As she aged, she took delight in the continuity of the
details in the house, securing her closet every day with a rare
late-17th-century lock.

Few other presidents of the Royal
Agricultural Society or the Royal Smithfield Club could recite a flock's
afflictions as she could – "Orf scrapie, swayback, blackleg, water mouth
or rattlebelly, scab and footrot, scad or scald" – or work with a
sheepdog, and she appreciated a whippet or two about her feet.

Debo's book Farm Animals (1991) featured
rare breeds of fowl, Buff Cochins and Wesummers, which she raised; the
Chatsworth farmyard was a teaching aid for cityfolk. She liked to cite the boy
from a school in Sheffield who watched the
milking demo. "He gave me such a look and said, 'I think it's the most
disgooosting thing I've ever seen in me life, I'm never going to drink milk
again."

The Devonshire marriage weathered
revelations during an Old Bailey trial in 1985 that the Duke, for all the
family motto "secure by caution", had been careless with his
chequebooks while furnishing the London flats of young female acquaintances. He
was generous to his Duchess, too, over the years commissioning a collection of
bejewelled insect brooches, which she wore pinned to ribbons as they left quite
dreadful holes in frocks. In 1999 she was made a DCVO, a dame in the Royal
Victorian Order. At the 50th anniversary of the couple's accession to the ducal
title, Debo swanned into the marquee in a costume created for a Victorian
duchess at a 19th-century Chatsworth thrash: she found its whaleboning very
supportive.

Following her husband's death in 2004 she
remained active as a writer, producing a memoir, Wait for Me!, in 2010. Three
of her children died at birth. Her son Peregrine succeeded to the dukedom, and
she is also survived by her daughters Emma and Sophia.

• Deborah Vivien Cavendish, Dowager Duchess
of Devonshire, stately home owner and writer, born 31 March 1920; died 24
September 2014